Sub up, back, or sideways.

[Knocker]

In the back of my 4Runner I was planning on having my Mayhem 18 (pointed upward) in about 5.5 cubes tuned to 33 with a 9 inch round port (22 inches long, 11.5 sq. inches of port per cube) pointed back, but just realized I don't have the room to point it to the rear unless I want the port 1 or 2 inches away from the back wall. I now have the option of pointing it sideways or up. Is that a big deal? Or how about sub back and port up? Iknow bass is non-directional but was just under the impression that port-back was the way to go. I have a BC 5500 (plan on pushing 3500-4000 watts), a D7500, a D3400, a Singer 240A alt, and will be using all 2/0 OFC. This will be a daily driver.

[rockFord_Expedition]

That's tough, and is often vehicle dependant.

[Shenker]

From what research I have seen, typically the best sound from a sub stage in general is where the sub and port are as far away from the listener as possible giving the air the most room possible to travel (hence most people facing subs/ports to the back in the back of vehicles). I cant remember exactly which video I watched or who it came from but they experimented with different sub layouts in a car trunk, rear facing, side facing, and front facing. The results on term lab showed best results facing rear, and also a variety of people who were there to listen for quality of sound, voted best sound came from rear facing sub/port as well, described as cleaner, smoother, crisper lows. side facing came second in both categories, and front facing came last. now they didn't test upwards facing but I would say it wouldn't be much different from side facing. Keep in mind of course this testing was done with something like a 12" something on like 500w, not quite an 18" on 5500w but its just a general idea. I would say your best bet would be to point the sub and port up in the back, with the port right near the back of the vehicle. although i'm sure that sub back/port up would be just as effective. I personally don't think its worth choking your port off trying to make it face the rear. its tough to visualize which option would make the most air movement farthest back without seeing it for me, so you will have to do that because you know what your working with, but generally speaking, you do want air movement as far away from the listener as possible. just some food for thought, and rockford_expedition is right it can very vehicle dependent.

[Knocker]

Yeah I was just about to hit Home Depot and was measuring my truck to see if it would fit a sheet of MDF and realized it's much shorter (the truck) than I thought. With 34 inches to play with and a 22 inch port and having to keep the mouth of the inside end of the port at least 9 inches away from the wall I came up short since I need 9 inches from the outside mouth to the back of the truck too. Tried making the port diameter smaller for a shorter port but then didn't have as much port area as I want for my amount of power. Making the box smaller to increase the port area/box volume ratio just made the port longer again. Damn Catch 22. Been thinking about using a smooth 90 degree bend in the port and also some external squarish port designs... If I had an 8×10 external rectangular port would the hole cut in the box be 8x10? Possibly gonna look at more conventional slot ported designs but I was really trying to avoid that because of my limited knowledge of woodworking and understanding of slot port design. I was thinking that if I could use a good smooth bend in the pvc which might lower the tuning if it was too low I could see when the excursion was the lowest (tuning frequency) and shorten the port accordingly. I saw a similar video by Crutchfield about trunk sub placement. And yes I am positive this is almost always vehicle dependent. Acoustics, standing waves, etc. are gonna have an effect on everything. Hopefully I'll have this figured out by next week.

[Shenker]

Whats your max dimensions? I'm not a box building expert by any means, and I wont claim to be but I could point you in the right direction with a sketch-up model of an example of what you might need for a slot ported design. Another option is aeroports, I have never used them, I do know when properly used they displace very little air, flared ones provide good pressure loading and clean sound, easy to install/use, and are very easy to manipulate your tuning.

[Knocker]

My max dimensions are 38.75 inches wide (between wheel wells), 21 inches height, and 23 inches deep if there are not going to be any angles. That would be with the box tucked up against the back seats And leaving about 10 inches between the back of the box and the lift gate. I have a lot of power so I need enough port area to not have any port compression. My preferred tuning is 32-33. I prefer the box be between 5-6 cubes for power handling, plus with the Mayhem the response curve seems to be a bit flatter with the smaller box. I was also hoping to have one exterior blank wall wide enough to mount both amps at 9.5 inches wide each and was hoping to have the box either 38.75 inches wide to fill the wheel wells or 31.5 inches wide to fit my D7500 battery between the box and the wheel wells. I know that's a lot to ask but this all needs to fit and look good. I can tell by your build log that you take this shit seriously as well. I was looking at aero ports but they don't seem to make anything bigger than 6 inches in diameter (except Psychoport, who seem to be closed for some reason) and I need more port area than that. I was however planning on flaring the ends of my 9 inch pvc tube using a heat gun or bell mouths.

- By the way, if anyone reading this can see any flaws in my "knowledge", please point it out to me because this box shit is new to me.

[Shenker]

Sounds good, I'm at work today but when I get home I'll run some numbers in a box calc and see what I can't come up with for you.

[Knocker]

Awesome. And if you're having any trouble, the width of 31.75 and height of 21 are absolute, but the depth of 23 inches could be extended a little if you really had to. My box design software on my Android tablet is decent and gives a cut sheet but that's about it. No visual representation or any of that. I kind of miss having a real computer. Thanks man.

[coh33dkill3r]

Hopefuy I don't catch any hell for posting this from another site but you could try this and possibly fit the 9" port back

http://www.caraudioclassifieds.org/forum/direct-sound-solutions/177623-long-round-ports-small-enclosures.html

[Knocker]

That's really interesting. It looks like as long as the area of the space between the inner and outer tube is the same as the port area of the original tube it ends up being an extension of the tube.